As molecular-assembly growing methods, especially methods of growing a single-molecular assembly, a large number of methods, such as a liquid-phase epitaxial (LPE) method, a molecular-beam epitaxial (MBE) method, a chemical vapor transport (CVT) method, and a chemical vapor deposition (CVD) method, have been proposed. The use of these methods enables to obtain a relatively large single crystal or a single crystal film. A method of growing a crystal by an electrolytic method, which is a crystal-growing method utilizing an electrolytic reaction, has also been known (e.g., Lectures on Experimental Chemistry 12, Functionality of Substances, 4th Edition, pp. 40-45, Maruzen).
In Japanese Patent Application Laid-Open No. 6-321686, a method of manufacturing a metallic-atom-doped carbon cluster compound, characterized in that a single-molecular assembly of the compound is grown in an organic solvent in which an organic salt of a metal and carbon clusters are dissolved in a cathode side using an electrolytic crystal method.
When a molecular nano-wire is manufactured, the manufacture using a molecular vapor deposition method of a molecular beam method in ultra-high vacuum has been known. A method of manufacturing a molecular nano-wire by arranging dendrimers or closed-shell molecules, and a method of manufacturing a carbon nano-tube have also been known.
However, conventional electrolytic methods aim at forming crystals as large as possible, but not forming nano-scale molecular assemblies. Also since conventional electrolytic methods aim at forming crystals of a milli-scale or larger, they have a problem that it is difficult to form high-purity crystals. The carbon cluster formed using the method of forming a carbon cluster described in Japanese Patent Application Laid-Open No. 6-321686 also has the size of millimeter units, and is not controlled at a molecular level. The invention described in the same patent aims at forming a larger single crystal, and not at forming a nano-scale molecular assembly as in the present invention. As a result, although the invention described in the same patent uses an electrolytic crystal growing method to form a molecular assembly, it does not use electrodes with a narrow gap between the electrodes, and only a molecular assembly of a millimeter level or a sub-millimeter level can be formed.
Also when a nano-wire is manufactured using a molecular vapor deposition method or a molecular beam method under ultra-high vacuum, the vacuum apparatus is expensive and complicated, and a large-scale apparatus is required. There is also a problem of requiring labor even for producing a vacuum. In a molecular vapor deposition method or a molecular beam method under ultra-high vacuum, there is a problem that a functional group to cause interaction such as hydrogen bonds must be introduced between molecules or between molecules and the substrate in order to fix molecules with each other or molecules with the substrate. When a nano-wire is formed in vacuum, there was a problem that the properties of the nano-wire change due to oxidation or the like when the vacuum is broken. Since conventional nano-wires (molecular assemblies) were assemblies of molecules that had a closed-shell structure (a structure having two electrons in a HOMO (highest occupied molecular orbital), and no molecules that had SOMO (semi-occupied molecular orbital), there was a problem that only nano-wires that had low electron mobility and poor conductivity were obtained.
Furthermore, the providing of electronic circuits having nano-scale or sub-micro-scale functional sites, and electronic devices using such electronic circuits has been demanded.